48 DISCOVERMAGAZINE.COM
ICECUBE/NASASPACE
Powerful black holes, the solar system, faraway galaxies and more spill
their secrets. BY BILL ANDREWS
Learning to
Speak Neutrino
We’re iguring out how to see
the cosmos in a new way. For
centuries, humans learned about
the universe with just their eyes,
observing in visible light. We
eventually developed technology
to see in other wavelengths of
light — infrared, X-ray, gamma
ray — to discover even more
about the universe. Now, thanks
to two papers in Science in
July, astronomers can see with
neutrinos, too.
Neutrinos are thought of as
ghostly particles because they
interact so little with matter.
Trillions of the subatomic things
pass through your body and the
rest of the planet every second,
without disturbing any atoms.
This indifference to anything in
their way makes them ideal for
astronomers hoping to understand
the extreme environments that
can produce them and other
interesting but easily blocked
particles, like cosmic rays and
extremely energetic light.
“Light is whatever’s on the
outside of an object,” says
University of Maryland physicist
Erik Blaufuss, a co-author on
both papers. The sun’s light, for
example, emerges at its surface,
whereas solar neutrinos are
created deep within the star.
“Neutrinos really are deeper
probes on the internal workings
of the object.”
The hard part is actually
catching a neutrino, especially one
from a distant source, but that’swhat the IceCube observatory
in Antarctica did in September- A particularly energetic
neutrino got caught in the cubic
kilometer of ice that serves
as the observatory’s detector.
Astronomers soon realized they
could trace its trajectory back
to a speciic type of black hole,
known as a blazar, in a galaxy
3.7 billion light-years away. (See
“Staring Down the Barrel of a
Black Hole,” opposite page.)
That alignment could have just
been coincidence, but then other
observatories reported a surge
in energetic gamma rays coming
from the same black hole around
the same time as the neutrino’s
arrival. The overwhelmingNeutrinos are
thought of as ghostly
particles because
they interact so little
with matter.
Astronomers detected
the exotic particles
spewed by a blazar, as in
this fanciful rendering.